The present disclosure starts from a method described in the earlier German Patent Application 10 2011 076 809.2 for the complete machining of unmachined journals/pins and flat shoulders of forged or cast blanks for a crankshaft. According to this earlier proposal, the machining of the crankshaft starting from the blanks 10 was improved by a novel distribution of the processes of turning, rough grinding and fine grinding between the individual regions of the crankshaft. More specifically, the procedure was as follows:
a) the flat shoulders associated with the central bearing journals are machined first of all by turning,
b) the central bearing journals and the crankpins are then rough-ground, the former without the flat shoulders thereof and the latter with the flat shoulders thereof and, finally,
c) after this, the central journals and the crankpins are finish-ground to the final size.
Among the resulting advantages are that an oversize remaining after step b is smaller than an oversize required for conventional finish-grinding of journals/pins and flat shoulders. Subsequent finish-grinding is therefore accomplished more quickly and with less wear on the grinding disks than in the conventional procedure, according to which the flat shoulders on the central bearing journals must always be rough-ground.
According to the earlier German Patent Application 10 2011 076 809.2, it had already been recognized that the hitherto conventional rough grinding involved in the machining of the large flat shoulders on the central bearing journals could be replaced by a turning process. On the other hand, the opinion was that rough grinding would have to be retained for the machining of the flat shoulders laterally surrounding the crankpins and situated on the webs of the crankshaft. In this context, it was expressly explained how difficult it would be to create a turning machine by means of which a crankshaft region that moved eccentrically during the rotation of said crankshaft could be machined economically and accurately by turning. Moreover, the flat shoulders on the crankpins are significantly smaller than the flat shoulders on the central bearing journals. The conventional procedure of rough-grinding the flat shoulders of the crankpins using the broad sides of the grinding disks, by means of which the crankpins themselves and, if appropriate, the undercuts were also machined, was therefore retained.